The broad objective of this research is to determine characteristic properties of highly purified cardiac and smooth muscle alpha-actinin, tropomyosin, and 56,000 intermediate filament protein, of their interactions with other myofibrillar proteins, and of the structures in which they are located in order to increase our understanding of the function of these three proteins and our knowledge of the cardiac and smooth muscle contractile systems. Specific objectives and methods of the proposed research include: (1) determination of the molecular parameters of smooth muscle alpha-actinin, tropomyosin, and 56,000 dalton protein; (2) a thorough biochemical comparison of smooth muscle alpha-actinin and tropomyosin with the corresponding proteins isolated from cardiac and skeletal muscle; (3) study of the interaction of alpha-actinin (in both cardiac and smooth systems) with the other myofibrillar proteins, particularly actin, tropomyosin, and 56,000 dalton protein, in order to help clarify the biological roles of alpha-actinin,tropomyosin, and 56,000 dalton protein; (4) determination of the exact location of alpha-actinin in the intercalated disc region and amorphous or Z-lattice filaments of cardiac muscle, and localization of alpha-actinin and tropomyosin in smooth muscle by antibody-binding, proteolytic dissection and selective extraction techniques coupled to electron microscopic experiments; and (5) determination of the complete composition and the structural arrangement of proteins in the dense body-intermediate filament complex of smooth muscle. BIBLIOGRAPHIC REFERENCES: Okitani, A., D.E. Goll, M.H. Stromer, and R.M. Robson. 1976. Intracellular inhibitor of a Ca 2+ - activated protease involved in myofibrillar protein turnover. Federation Proc. 35: 1746. Stromer, M.H., L.B. Tabatabai, R.M. Robson, D.E. Goll, and M.G. Zeece. 1976. Nemalin myopathy, an integrated study: selective extraction. Exptl. Neurol. 50: 402-421.